How many pucks to get to 30 to 50 ppm cya

[chem geek]

Unfortunately, it will take time for the Trichlor to dissolve to give you the CYA you need. If you want to get CYA into the pool faster while adding chlorine at the same time, then you could use Dichlor powder/granular. For every 10 ppm Free Chlorine (FC) added by Dichlor, it also increases CYA by 9 ppm. So in 13,500 gallons that's about 7 pounds of Dichlor to get you to 30 ppm and about 11 pounds of Dichlor to get you to 50 ppm.

However, since you want to fight an algae bloom, I'd only add a smaller amount of CYA, say around 20 ppm, and then use chlorinating liquid or bleach to maintain the shock level of FC (see this chart). You'll need a lower chlorine level to fight the algae bloom this way and it will go a little faster.

After you clear you pool of algae, your can use more Dichlor or even Trichlor pucks or pure CYA at that point to keep adding to CYA.

Richard

[waterbear]

You might actually find it's less expensive and easier to just buy CYA (conditioner or stabilizer) and add the required amount to your skimmer and then use bleach to chlorinate.

[Poconos]

If you go the puck route then be careful of the contents. Anything that says multi-purpose probably has copper or some other undesirable ingredient. Check the label because I've seen buckets of the stuff at Sam's Club that looked identical according to the ingredient label but one kind was more expensive and said multi something on the bucket. As I recall the clorine concentration was also lower for the multi-purpose stuff.
Al